Validating a Simulation Model for Laser-Induced Thermotherapy Using MR Thermometry

TL;DR

Whether temperature measurements obtained from MR thermometry are accurate and reliable enough to aid the development and validation of simulation models for Laser-induced interstitial thermotherapy (LITT) is investigated.

Abstract

Laser-induced interstitial thermotherapy (LITT) is applied to ex-vivo porcine livers. An artificial blood vessel is used to study the cooling effect of larger blood vessels in proximity to the ablation zone. The same setting is simulated using a model based on partial differential equations (PDEs) for temperature, radiation, and tissue damage. The simulated temperature distributions are compared to temperature data obtained from MR thermometry. The study shows that the quality and resolution of the thermometry data is sufficient to validate and improve modeling approaches. Furthermore, the data can be used to identify missing model parameters as well as the exact placement of the laser applicator in relation to the imaging plane.

Figures (6)

• Figure 1: MR imaging of the experimental setup in axial (a) and coronary (b) orientation. MR images show the liver in the center (1), the agarose gel phantoms in the periphery (2), the laser applicator (3), the plastic tube (4) passing through the liver (partial representation of the plastic tube in a), and bloodless vessels (5).
• Figure 2: Sketch of the computational domain $\Omega$ and the boundary decomposition: radiating surface of the applicator $\Gamma_\text{rad}$, cooled surface of the applicator $\Gamma_\text{cool}$, surface of the artificial blood vessel $\Gamma_\text{vessel}$, and ambient surface of the liver $\Gamma_\text{amb}$.
• Figure 3: Case 1: Comparison between measured $T_\text{exp}$ and simulated temperature $T_\text{sim}$. The standard deviation $\sigma$ is computed within the dashed box, disregarding the hatched area where the measurement is unreliable due to coagulation.
• Figure 4: Case 2: Comparison between measured $T_\text{exp}$ and simulated temperature $T_\text{sim}$. The standard deviation $\sigma$ is computed within the dashed box, disregarding the hatched area where the measurement is unreliable due to coagulation. Note: For this case artifacts in the MR thermometry data likely result in faulty temperature measurements.
• Figure 5: Case 3: Comparison between measured $T_\text{exp}$ and simulated temperature $T_\text{sim}$. The standard deviation $\sigma$ is computed within the dashed box, disregarding the hatched area where the measurement is unreliable due to coagulation.